Smoking articles

ABSTRACT

The invention relates to a smoking article ( 1 ) having a high proportion of non-combustible, inorganic material and a relatively low level of visible sidestream. The smoking article comprises a substantially non-combustible, wrapper ( 5 ) which extends along the full length of the smoking material rod and enwraps a combustible fuel source ( 6 ) and aerosol generating means ( 7 ), both of which extend substantially along the length of the smoking material rod. Various suitable fuel source system and aerosol generating systems are described. The article has a visible burn line which advances along the article and produces an ash which can be removed by the smoker in the normal way.

[0001] The present invention relates to smoking articles, and inparticular to smoking articles which have an other than conventionalstructure and combustion regime, yet which have the outward appearancesimilar to a conventional smoking article.

[0002] Many attempts have been made to produce a smoking article whichprovides the smoker with an aerosol which is similar to tobacco smoke.Some ideas have centred on generating an aerosol vapour from an aerosolgenerating means by heating the aerosol generating means with asurrounding fuel source, such as cut tobacco. Smoke from the fuel sourceis prevented by a smoke barrier from reaching the smoker's mouth, whilstthe aerosol vapour can pass to the smoker. These can be seen in U.S.Pat. No. 3,258,015 (Ellis) and U.S. Pat. No. 3,356,094 (Ellis). Thefirst of these proposed a smoking article having an outer cylinder offuel with good smouldering, characteristics, preferably cut tobacco orreconstituted tobacco, surrounding a metal tube containing tobacco,reconstituted tobacco or other source of nicotine and water vapour. Asubstantial disadvantage of this article was the ultimate protrusion ofthe metal tube as the tobacco fuel was consumed. Other disadvantagesinclude the formation of substantial tobacco pyrolysis products andsubstantial tobacco sidestream smoke. This design was later modified inthe second patent mentioned above by employing a tube made out of amaterial such as inorganic salts or an epoxy bonded ceramic, whichbecame frangible on heating and was discharged as an ash by the smoker.In this invention also there are substantial tobacco pyrolysis productsand, because of the combustion of tobacco, visible sidestream smoke.

[0003] Aerosol inhalation devices such as European Patent Applications,Publication Nos. 0 174 645 and 0 339 690 describe means of using heattransfer from a fuel element to physically separate aerosol generatingmeans. The main feature of these inventions is that the aerosolgenerating means is always physically separate from the fuel element andis always heated by heat transfer from a heat conducting member, neverburned. To this end the fuel element is always short, located to one endof the smoking article and kept out of direct contact with the aerosolgenerating means.

[0004] Other and mainly more recent devices have included GB 1 185 867(Synectics), U.S. Pat. No. 5,060,667 (Strubel) and EPA 0 405 190 (R. J.Reynolds). In all of these devices the patentee has arranged the fuelelement as an annulus around aerosol generating means.

[0005] GB 1 185 857 provided a substantially inorganic smoke of readilyabsorbable silts to the smoker and produced an ash which could beremoved in normal fashion by the smoker. However, the smoking article ispresumed to have given off an amount of visible sidestream smoke becauseof the cellulosic components within individual items of the smokingarticle.

[0006] U.S. Pat. No. 5,060,667 provided a co-axially arrangedtobacco-containing fuel element encircled by a metallic heat transfertube with a flange portion at the end to be lit in order to preventsmoke from the burning tobacco from passing through the flavour sourcematerial circumscribing the heat transfer tube. Only aerosol from theflavour source material passes to the smoker. The device does not burndown and tobacco material is combusted, as well as providing the flavoursource material, thereby producing visible sidestream smoke andutilising a high percentage of a costly item such as tobacco.

[0007] EPA 0 405 190 seeks to provide a smoking article which providesthe user with the pleasures of smoking by heating without burningtobacco. Most of the articles comprise an annular carbonaceous fuelsegment, a physically separate aerosol generating means disposedconcentrically within the fuel segment, a barrier member between thefuel segment and the aerosol generating means, which substantiallyprecludes fluid flow radially therethrough and which is disposable asthe smoking article is smoked, and a mouthend segment. As the fuelsource is disposed annularly around the aerosol generating means it isadvantageous to surround the fuel source longitudinally with aninsulating sleeve which may then be wrapped with a conventional wrapper.One alternative embodiment is postulated which comprises a coaxialcarbonaceous fuel source of slow burning rate encircled along itslongitudinal length by an insulation member, which in turn is encircledalong its length by tobacco wrapped in a paper wrapper. The tobacco isonly heated and not burnt, as in the other embodiments, but unlike theother embodiments of EPA 0 405 190 the device cannot burn down astobacco would then be burnt. No actual practical embodiment is describedand thus this embodiment appears to be an armchair, or paper, proposal.The patentees appear to have had some difficulty in reducing to practicethis particular concept. This concept also utilises considerable amountsof expensive tobacco, to provide the aerosol source material, which thesmoker never truly experiences.

[0008] U.S. Pat. No. 2,998,012 discloses a smoking article having anon-combustible wrapper of woven, glass fibres with one or more adhesivematerials, calcium carbonate to prevent flaming, propylene glycol as aplasticiser and a diatomaceous earth to render the wrapper impermeableand cooler to the touch. A disadvantage of this construction is that thewrapper still maintains a predominantly fibrous characteristic of wovenglass fibres. Such a wrapper would be unnaceptable for a commercialsmoking article. U.S. Pat. No. 4,961,438 discloses a smoking devicewhich does not burn down along its length which by means of asmouldering heat source heating air drawn into the device liberatesaerosol from an aerosol forming material disposed on a substrate. Thewrapper of the device is a non-combustible tube having high heatconductivity. Such high heat conductivity is undesirable for acommercial smoking article. The wrapper of the present invention seeksto overcome these deficiencies.

[0009] It is an object of the present invention to provide a smokingarticle which does not produce substantial tobacco pyrolysis products.

[0010] It is a further object of the present invention to provide asmoking article which exhibits very little visible sidestream smoke, andconsiderably less visible sidestream smoke than prior proposedconventional smoking articles comprising tobacco rods of cut tobaccowrapped in a paper wrapper containing a visible sidestream reducingcompound or being visible sidestream reducing paper.

[0011] It is another object of the invention to fulfil the aboveobjectives whilst maintaining a substantially conventional outwardappearance of a smoking article as we know the same today.

[0012] It is also an object of the invention to preserve the physicalelements of the smoking process, including the ashing of a cigarette toproduce an ash which can be removed by the smoker in the normal way.

[0013] The present invention provides a smoker article having a smokingmaterial rod comprising a substantially non-combustible wrapperextending substantially along the length of the smoking material rod andenwrapping a combustible fuel source extending substantially along thelength of the smoking material rod and aerosol generating meansextending substantially along the length of the smoking material rod.

[0014] As used herein the terms ‘smoking material rod’ or ‘smokingmaterial’ are merely intended to mean that part of the smoking articlewhich is contained within the substantially non-combustible wrapper andshould not have imported therein any association as to thecombustibility or otherwise of individual components of the rod of thesmoking material.

[0015] The present invention further provides a smoking article having asmoking material rod comprising a substantially non-combustible wrapperextending substantially along the length of the smoking material rod andenwrapping a combustible fuel source extending substantially along thefull length of the smoking material rod, and aerosol generating meansbeing disposed between the fuel source and the wrapper and extendingsubstantially along the length of the smoking material rod.

[0016] The present invention provides a substantially non-combustiblesmoking article wrapper comprised of predominantly non-combustibleinorganic filler material, a binder, optionally a plasticiser, andoptionally a small amount of cellulosic fibre material.

[0017] Preferably the non-combustible inorganic filler material is aparticulate material and even more preferably is a non-metallicmaterial.

[0018] This invention also provides a method of producing asubstantially non-combustible smoking article wrapper comprisingpredominantly non-combustible inorganic filler material and a binder,the method comprising producing a mixture of the non-combustibleinorganic filler material and a binder, extruding the mixture to providea hollow tube, and contacting the hollow tube with a material whichcauses the hollow tube to set rapidly.

[0019] The material which causes the hollow tube to set rapidly may be awater scavenging substance which removes water contained in theextrudate. Alternatively the material may be a solution which renders asoluble binder in the mixture insoluble, or a hydrophilic substancewhich removes water from an aqueous-containing mixture.

[0020] The present invention also provides a smoking article fuel sourceof substantially the whole length of a smoking article, the fuel sourcecomprising carbonaceous material, an inorganic non-combustible binderand optionally a burn promoter.

[0021] The present invention provides a smoking article fuel source ofsubstantially the whole length of a smoking article, the fuel sourcecomprising carbon, non-combustible inorganic filler material, organicbinder, optionally plasticiser and optionally inorganic binder.

[0022] The present invention provides smoking article aerosol generatingmeans comprising a non-combustible inorganic filler material, aerosolforming means, and an organic or inorganic binder.

[0023] The present invention also provides a smoking article aerosolgenerating means comprising an organic filler material, aerosol formingmeans, an organic binder and optionally a non-combustible inorganicfiller material.

[0024] The present invention provides a smoking article aerosolgenerating fuel source comprising a non-combustible inorganic fillermaterial, aerosol forming means, an organic or inorganic binder andcarbon.

[0025] The present invention further provides a smoking article aerosolgenerating fuel source comprising organic filler material, optionally anon-combustible inorganic filler material, aerosol forming means,organic binder and carbon.

[0026] Substantially Non-Combustible Wrapper

[0027] Preferably the substantially non-combustible wrapper is comprisedof predominantly non-combustible inorganic filler material. The term‘predominantly’ as used herein means at least about 65% and usually 70%.The inorganic filler material advantageously yields very little orsubstantially no visible sidestream smoke when the smoking article islit. Preferably the non-combustible wrapper comprises at least 80%, andmore preferably at least 90% inorganic filler material by weight of thewrapper. Advantageously the non-combustible inorganic filler material isone or more of perlite, vermiculite, diatomaceous earth, colloidalsilica, chalk, magnesium oxide, magnesium sulphate, magnesium carbonateor other low density, non-combustible inorganic filler materials knownto those skilled in the art.

[0028] The non-combustible wrapper may comprise a small amount ofcellulosic fibre material. Preferably the fibre material comprises lessthan 10%, more preferably less than 5%, and even more preferably lessthan 2% by weight of the non-combustible wrapper. Most advantageouslythe fibre material is not present in the wrapper.

[0029] Preferably the wrapper comprises a binder and/or a plasticiser.These components may be present at up to 30% by weight of the wrapper.Advantageously the binder is not present at more than 25% by weight ofthe wrapper. The exact proportions will depend on the tastecharacteristics, acceptable visible sidestream smoke emission andstrength of the desired product, and the processing techniques used. Thebinder may be present at about 8-10% by weight of the wrapper, althoughit may be present at about 5% or less by weight of the wrapper. Thebinder may be organic binders, for example, cellulose derivatives, suchas sodium carboxymethylcellulose, methyl cellulose,hydroxypropylcellulose, hydroxyethyl cellulose or cellulose ethers,alginic binders including soluble alginates such as ammonium alginate,sodium alginate, sodium calcium alginate, calcium ammonium alginate,potassium alginate, magnesium alginate, triethanol-amine alginate andpropylene glycol alginate or insoluble alginates which can be renderedsoluble by the addition of solubilising agents, such as ammoniumhydroxide. Examples of these include aluminium, copper, zinc and silveralginates. Alginates which are initially soluble but which, duringprocessing, undergo treatment to render them insoluble in the finalproduct may also be used, e.g. sodium alginate going to calcium alginate(see below). Other organic binders include gums such as gum arabic, gumghatti, gum tragacanth, Karaya, locust bean, acacia, guar, quince seedor xanthan gum, or gels such as agar, agarose, carrageenans, fucoidanand furcellaran. Pectins and pectinaceous materials can also be used asbinders. Starches can also be used as organic binders. Other suitablegums can be selected by reference to handbooks, such as Industrial Gums,Ed. Whistler (Academic Press). Combinations of the above may also beused. Inorganic non-combustible binders, such as potassium silicate,magnesium oxide in combination with potassium silicate, or some cements,for example, and mixtures thereof, may be used.

[0030] The wrapper, although not giving much, if any, visible sidestreamsmoke, does produce ash of an acceptable colour and quality. The smokingarticle also has a visible burn line which advances along the articleand enables the smoker to determine whether the article is alight and tomonitor the smoking process. The visible burn line may be formed as aresult of burning the organic binder. Alternatively, colour changingcompounds can be included in the wrapper composition. Colourants whichgive the wrapper an other than white colour may also be included. Thesecolourants may also change colour as heating occurs, providing a visibleburn line, e.g. CuSO4.5H₂O.

[0031] The nature of the binder selected will also determine thepermeability of the outer wrapper. Binders, such as sodiumcarboxymethylcellulose and propylene glycol alginate, have been found tobe particularly-effective at producing an outer wrapper sufficientlypermeable to sustain combustion of the fuel source within the wrapper.The latter binder gave the more permeable outer for the same outerwrapper composition. Hydration time of some binders can play a part indetermining the efficacy of the binders. Conventionally understoodstrong binders such as hydroxypropylcellulose can be used at lowerlevels to increase the wrapper permeability but this has to be balancedagainst the strength of the wrapper.

[0032] The plasticiser may be present in the wrapper at up to 20% byweight thereof. The plasticiser is preferably present at about 10% orless, preferably 5% or less, by weight of the wrapper. The plasticisermay be glycerol, propylene glycol, or low melting point fats or oils forexample. Depending on the method of production selected for thewrappers, the plastisicer may be absent from the wrapper composition.The plasticiser helps in the drying stages of the wrapper to preventshape distortion, particularly if direct heat, e.g. hot air, is thedrying medium. The amount of plasticiser, binder or other organic fillermaterial will affect the appearance of the burn line, i.e. the burn linewidth, and the amount of visible sidestream of the article. Preferablythe width of the burn line is not greater than 10 mm, is preferably notmore than 5 mm and more preferably is between 2-3 mm in width. The widthof the burn line depends on the composition of the burnable material inthe article.

[0033] The wrapper may comprise materials which provide an odour to anysidestream smoke which may come from the article. Suitable deodorisersinclude citronellal, vanillin and geraniol, for example.

[0034] The wrapper may be formed by producing a thick slurry of thewrapper components, coating the slurry about a rotating mandrel, andremoving excess moisture by physical or chemical means. Alternatively,the slurry may be cast as a sheet on a drum or band caster, or extrudedas a hollow tube, through a ‘torpedo’ die-head, for example, which has asolid central section, or extruded as a sheet material. The slurry couldbe sprayed, coated or pumped onto a suitably shaped fuel/aerosolassembly.

[0035] The extrusion process is suitably carried out at a pressure whichdoes not detrimentally affect the wrapper permeability and is suitablynot greater than 3-4 bar (300-400 kPa) at the extruder die of a ramextruder, for example, and not more than 9 bar (900 kPa) for an APVBaker Perkins screw extruder. The extrusion process may require foamingto occur at the die exit to produce a cellular structure, in which casegreater pressure can be exerted, at the die, whilst retainingpermeability.

[0036] After extrusion or coating the hollow extrudate or coated mandrelis suitably subjected to heat at or exit the die to drive off excessmoisture. The wrapper slurry may comprise a heat activated binder, suchas potassium silicate, magnesium oxide, or hydroxypropylcellulose attemperatures above 40-50° C., for example. Subjecting the coated mandrelor hollow extrudate to heat would activate the binder causing thewrapper to set. Infra-red or microsave heating is advantageous as directheating, e.g. the use of hot air blowers, can affect the shape of theextrudate, especially at temperatures of greater than 100° C.

[0037] Extrusion may be carried out using a single or double screwextruder, a ram extruder or slurry pump.

[0038] The wrapper suitably has a thickness within the range of 0.1-1.0mm, although 2-3 mm may be desirable. The thickness required depends onthe weight and permeability of the wrapper. Thus, a dense thin wrapperor a thick low density wrapper could be provided, depending on thecomposition of the wrapper materials.

[0039] Alternative setting methods for the wrapper include the use ofwater scavenging substances. These substances remove water from thewrapper slurry thereby, in effect, drying the wrapper. For example,light magnesium oxide can be in the wrapper slurry mixture at up to 45%by weight of the dry slurry constituents, depending on the residencetime in the extruder and the temperature in the extruder. The additionof magnesium oxide can also have advantageous visible sidestreamreducing effects. Alternatively, the wrapper material can be extrudedinto an ethanol bath, or other strongly hydrophilic substance, theethanol scavenging the water from the extrudate. A further alternativeis the precipitation of an insoluble alginate from a soluble alginate inthe extruded wrapper. This can be achieved by, for example, extruding ahollow tube of, for example, sodium alginate-containing wrapper materialinto a bath of simple electrolyte(s), for example, 1.0M calcium chloridesolution. The calcium ions substitute for the sodium ions and cause theextrudate to set extremely quickly. In the latter two methods, sprayingof the water scavenger onto the extrudate or wrapper sheet may becarried out instead of passing the extrudate into a bath.

[0040] Some precipitation can be achieved by adding a sub-critical levelof a precipitating agent into the extruder barrel, then completelyprecipitating the structure by raising the level of the precipitatingagent post extrusion. Other precipitation methods include precipitationof the extrudate into a highly ionic electrolyte bath or into a watermiscible non-solvent for the alginate.

[0041] A further method includes, as briefly mentioned above withrespect to the binders, use of a conventionally insoluble alginate asthe binding material by rendering it soluble with a solubilising agentand then setting of the wrapper structure by removal of the solubilisingagent or addition of a sequestering agent.

[0042] These methods may be used sequentially, e.g. the wrapper may beset by precipitating a soluble alginate containing wrapper material in abath containing calcium ions. The extrudate may be subsequently passedinto a bath of water scavenging agent, such as ethanol, and then heatedto drive off liquid residues. Alternatively, after setting the wrappermay be dried using the methods described above.

[0043] These methods are particularly effective for achieving a goodshape to the extrudate because of the speed of the reaction and the lackof volume reduction in the processes, particularly the drying stages.

[0044] The wrapper may have a rigid structure, although we have foundthat flexible wrappers can be produced using sodium alginate as thebinder, which is then precipitated to form calcium alginate and thenslowly dried. Flexibility is advantageous in terms of the increasedrobustness of the product during machine and manual handling.

[0045] The wrapper suitably has a air permeability within the range of1-300 Coresta Units (cc/min//cm²/10 cm WG). Permeability can becontrolled by a number of methods, such as coating an extrudate with afilm forming or other permeability reducing agent. Alternatively,sacrificial molecules can be introduced into the wrapper mixture, whichmolecules can be removed after the formation of the structure bymoderate temperature or chemical reaction to increase the permeabilityof the wrapper structure.

[0046] Alternatively, the wrapper may be a cellulose-based wrapper, suchas conventional cigarette paper, which has been treated to prevent thewrapper from burning and thereby producing visible sidestream smoke.Preferably the treated wrapper will char and therefore provide a visibleburn line. The paper should also produce an ash which can be knocked offby the smoker.

[0047] The ashing characteristics of the wrapper should be such that,unburnt, the wrapper is strong enough or flexible enough to resistdigital pressure prior to, and during smoking, but upon thermaldegradation of the wrapper the structure is considerably weakened,leaving an ash which can be readily disintegrated by pressure or aflicking movement. Some wrappers may require ash charring agents whichchar to leave some black residue to simulate conventional cigarette ash.

[0048] Fuel Source

[0049] Preferably the fuel source extends continuously from the mouthend of the smoking article to the lighting end thereof, excluding anyfilter or mouthpiece element. In the alternative, the fuel source maycomprise a number of sections closely located so that burning of thefuel source does not cease.

[0050] Advantageously, the end of the article to be lit has theappearance of a conventional article. Suitably the end of the smokingarticle at the end to be lit is of a tobacco-like or dark colour, e.g.brown.

[0051] The fuel source may be provided by three distinct systems, butoverlap may occur between them. In these systems the fuel source isphysically discrete from the aerosol generating means.

[0052] When physically discrete from the aerosol generating means and inthe form of a rod, in a first system the fuel source is suitablyprepared from carbonaceous material by pyrolysing wood, such as rods ofbalsa wood, cotton, rayon, tobacco or other cellulosic containingmaterial, which are prepared to a shape which is particularly useful inthe present invention. In this system, the fuel source comprises atleast 85% by weight pyrolysed carbonaceous material. Preferably the fuelsource comprises at least 90% carbonaceous material. A burn promotersuch as, for example, potassium nitrate, potassium citrate or potassiumchlorate, is also advantageously present at 10% or less by weight of thefuel source. Other suitable burn promoters would be known to thoseskilled in the art. Alternatives for an almost wholly carbon-containingsystem include the use of carbon fibres or carbon aerogels.

[0053] The term ‘carbon’ as used herein can be taken to cover a materialwhich is substantially solely carbon and any carbon precursors, such ascarbonaceous material. As used herein the term carbonaceous includesmaterial which has been pyrolysed, which material preferably containscarbon, although some incomplete combustion products may still bepresent. Ready pyrolysed coconut fibre may, for example, be thecarbonaceous material from which carbon is derived.

[0054] In a second system, the fuel source may be a substantiallyinorganic system and comprise an inorganic, non-combustible binder,selected from the list outlined above with respect to the wrapper, forexample, Portland cement, or potassium silicate. The binder may bepresent within the range of 10-65% by weight of the fuel source. Thebinder is advantageously present in an amount of less than 40% by weightof the fuel source. The fuel source may also comprise 5-20% of a burnpromoter, preferably less than 10%, by weight of the fuel source. Thefuel source may comprise 5-70% carbon, advantageously at least 55%carbon, and more suitably at least 60% carbon by weight of the fuelsource. However, we have found that acceptable combustioncharacteristics can still be maintained with about 30% carbon, 60%inorganic, non-combustible binder and less than about 10% burn promoterwhen the fuel source is provided as a rod. A proportion of inorganic,non-combustible filler in the range of 0-60% may also be incorporated inthis alternative to reduce the density of the fuel source or to improvethe strength of the fuel source.

[0055] The fuel source in this instance may, for example, be a shapedrod of carbon having a porous structure to sustain continuous combustionthroughout the length of the fuel source. Shaping techniques which donot disadvantageously lose water during shaping of the rod arepreferred. Shaping of a thick slurry comprising carbon and a binderwithin a hollow tube and removing the shaped rod from the tube after acuring or setting stage is one method of fuel source production.Alternatively, an extrusion process may be used.

[0056] In the third system, the fuel source is a partially organicsystem and comprises 15-70% carbon, 84-5% non-combustible inorganicfiller material such as, for example, one or more of the inorganicfiller materials listed above with respect to the wrapper, 0-5%plasticiser, such as one or more of low melting point fats or lowmelting point oils, and 1-20% organic binder, such as cellulosic,alginic or pectinaceous binders, for example, and/or the other organicbinders described above with respect to the wrapper. A mixture ofinorganic or organic binders may be used, the inorganic binder beingpresent within the range of 0-20% by weight of the fuel source. Theplasticiser is included to improve the mechanical strength andflexibility of the fuel source and the amount present together with theamount of organic binder, should not provide a significant quantity ofmainstream smoke. A high level of organic binder might be utilisable ifthe binder produces a low level of mainstream smoke, i.e. particulatematter. The amount of carbon is subject to the type and amount of binderand/or filler utilised, thus the range above should not be consideredtoo limiting. The amount of carbon required will also depend on thecomposition of the outer wrapper. Furthermore, at low levels of carbonusage the outer wrapper will need to be more permeable than at highercarbon levels. Most suitably the carbon is present in the range of25-35%.

[0057] Extrusion may be a low pressure extrusion through a nozzle usinga driving force not substantially greater than atmospheric pressure, ora high pressure extrusion process. Foaming of the extrudate to achieve acellular structure may be required, particularly in the second and thirdsystems, depending on final product design. In the second system,foaming could be achieved by the introduction of air entraining agentsinstead of a proportion of the inorganic, non-combustible binder and/orthe inorganic filler, if present. The air-entraining agents can bepowdered or liquid additives or porous particulate materials. In thethird system when foaming is required it may be achieved by the presenceof, for example, a polysaccharide expansion medium such as starch, andthe expanding effect of water under high temperature and pressure. Theexpansion medium would replace the binder or the plasticiser orinorganic filler, if present. Alternative expansion mediums, such aspullulan or other polysaccharides, including cellulose derivatives, maybe used. Other agents capable of causing foaming may be solid foamingagents, such as sodium bicarbonate, inorganic salts and organic acidsproviding in situ gaseous agents; propane or isobutane as organicgaseous agents; nitrogen, carbon dioxide or air as inorganic gaseousagents; and volatile liquid foaming agents, such as ethanol and acetone,for example. Polysaccharide expansion mediums are preferred because oftheir ease of usage and safety aspects.

[0058] Extrusion may produce thin elongate strands, which may belongitudinally arranged, or more solid thicker rods, preferablyco-axially located within the smoking material rod. In the first twoalternatives, i.e. the pyrolysed structure and the inorganic system, acentral rod could be replaced by several thinner strands. Extruded sheetmay also be produced, then shredded to produce cut filler similar to cuttobacco filler. These processes are all suitable for the production ofthe fuel source, the aerosol generating means and the combined aerosolgenerating fuel source to be described later. Band casting, heated drumcasting and other sheet making techniques can also be used.

[0059] In all of the above fuel source alternatives, except in thepyrolysed rod embodiment, 0-2% fibre is optional. This also applies tothose methods of preparation of aerosol generating means which involvecasting or paper making techniques.

[0060] Aerosol Generating Means

[0061] The aerosol generating means may be provided by three distinctsystems, but overlap may occur between them.

[0062] The first system may be a substantially inorganic systemcomprising 95-30% inorganic, non-combustible binder, such as thosebinders described above with respect to the fuel source, 0-65%non-combustible inorganic filler material, such as those materialsdescribed above with respect to the fuel source, and 5-30% aerosolforming means, as described below.

[0063] The second system may be a partially inorganic system comprising1-25% organic binder, 45-94% non-combustible inorganic filler materialand 5-30% aerosol forming means. The third system may be a partiallyorganic system comprising 1-25% organic binder, 1-94% organic fillermaterial, 0-93% inorganic filler material and 5-30% aerosol formingmeans. Preferably the aerosol forming means comprises 5-25% by weight ofthe mixture. These systems are intended to be substantiallynon-combustible. The inorganic filler material is therefore selected, incombination with the proportions of the other materials, to providesubstantially non-combustible aerosol generating means. Some inorganicfillers, such as perlite, magnesium hydroxide and magnesium oxide,readily serve to render the aerosol generating means non-combustible.Other fillers, such as chalk, at some incorporation levels, do notdetract from the combustibility of the aerosol generating means and assuch are unsuitable at those levels.

[0064] The organic filler material is preferably a material other thantobacco and may include inorganic salts of organic acids, orpolysaccharide material, and should provide smoke with an acceptabletaste characteristic.

[0065] These two systems represent two ends of a spectrum in whichinorganic and organic components of the binder and filler material canbe gradually substituted for one another. The third system may alsoincorporate an amount of expansion medium, such as described above, aspart of the organic filler material. An example of foamed aerosolgenerating means comprises 20% organic binder, 20% aerosol formingmeans, 15% starch as an expansion medium and 45% inorganic fillermaterial. The aerosol generating means may also comprise flavouringmeans.

[0066] A small amount of fibre material may also be required in theabove systems to assist in the formation of a sheet, depending on themanner of manufacture.

[0067] The aerosol generating means preferably comprises aerosol formingmeans, such as polyhydric alcohols, glycerol, propylene glycol andtriethylene glycol, for example, or esters such as triethyl citrate ortriacetin, or high boiling point hydrocarbons.

[0068] Flavouring agents in the smoking material rod are designed tocontribute towards an aerosol which has a unique but very acceptabletaste and flavour characteristic to the aerosol smoke. The taste andflavour may not necessarily be designed to imitate tobacco smoke tasteand flavour. Flavouring agents may include tobacco extract flavours,menthol, vanillin, toffee, chocolate or cocoa flavours, for example.Colouring means, such as food grade dyes, for example, or colourantssuch as liquorice, caramel or malt, or extracts thereof, may be used todarken the colour of the filler material. The presence of vermiculite orother inorganic material, such as iron oxide, may also give a darkercolour to the filler material of the smoking article.

[0069] Flavouring agents may also be incorporated on or into asubstrate, which may be the aerosol generating means and/or the fuelsource, at a location close to or at the mouth end of the smokingmaterial rod of the smoking article, or along the length of the smokingmaterial rod provided that they are not affected by combustiontemperatures. The percentages given above are given without the additionof any flavouring agent. These percentages will be consequently reducedby the addition of flavouring agents. Where inorganic or organic fillermaterial is present in the aerosol generating means or fuel source, thepercentages of these elements would be decreased as flavourantsincreased. Where filler material is not present, either the carbon oraerosol forming means would be consequently reduced as the flavourantsincreased.

[0070] As mentioned above, the aerosol generating means may be formed byconventional paper-making techniques or by extrusion techniques. Thesheet material may be cut or rolled. The inorganic filler materials ofthese systems can be used in the system mixtures without pre-treatmentstages before providing a complete aerosol generating mixture.

[0071] Aerosol Generating Fuel Source

[0072] As described above both of the fuel source and the aerosolgenerating means are kept substantially separate from one another, eachforming a distinct area of either fuel source or aerosol generatingmeans. In some instances though it may be advantageous to combine thetwo elements. This can be done by mixing physically discrete fuel sourceand aerosol generating material or by producing a totally combinedaerosol generating fuel source. In the first case, a preferredembodiment is mixing the fuel source as cut filler material with aerosolgenerating means as cut filler material. Thus, an aerosol generatingfuel source comprising a mixture of physically discrete individual cutfiller material is provided, which filler material extends the fulllength of the smoking material rod. This embodiment is particularlyadvantageous in that it can be made in a manner very similar toconventional cigarette making procedures by providing a mixture of cutfiller material to a cigarette making machine. In the second case,carbon is added to the aerosol generating means composition.

[0073] The aerosol generating fuel source may be provided by threedistinct systems, but overlap may occur between them. The first systemis a predominantly inorganic system comprising 0-35% inorganic fillermaterial, 5-30% aerosol forming means, 30-60% inorganic binder, 30-65%carbon and 0-10% burn promoter. The aerosol forming means is selectedfrom the group outlined above with respect to the aerosol generatingmeans. The other components are also to be selected from the respectivegroups outlined above with respect to the other elements of theinvention. This also applies to the systems described below.

[0074] The second system is a partially inorganic system comprising86-0% inorganic filler material, 5-30% aerosol forming means, 1-25%organic binder and 8-60% carbon.

[0075] The third system is a more organic system comprising 93-0%organic filler material, 0-93% inorganic filler material, 5-30% aerosolforming means, 1-25% organic binder and 1-60% carbon. The more organicsystem may be foamed by the presence of an expansion medium and/orexpansion agent, at the levels described above.

[0076] Preferably the aerosol forming means comprises 5-25% by weight ofthe mixture.

[0077] The binders and aerosol forming means for the above aerosolgenerating fuel sources may be any one or more of the binders or aerosolforming means exemplified above.

[0078] With the increase in organic components and the respectiveincrease in sidestream, the permeability of the outer wrapper must becontrolled to reduce the visible sidestream given off by this fuelsource composition or, as described below, sidestream reducing agentscan be added to the wrapper to reduce the amount of particulate matterforming the sidestream smoke. The thickness of the outer wrapper canalso be varied to reduce visible sidestream smoke.

[0079] Structure of Article

[0080] The smoking article may be provided in a number of physicalstructures. In all three fuel source systems the fuel source may beprovided as a longitudinally extending rod, strands or filaments,advantageously located co-axially of the smoking article. The rods,strands or filaments can be of various shapes, e.g. round, square, staror polygonal, all of which may be hollow or solid, and may be co-axiallyclustered. In the second and third system the fuel source may also be asheet material which can be cut to produce shreds. Material of the thirdsystem may also be rolled to the desired shape.

[0081] When the fuel source is provided as a central rod of eithercarbonised wood or an extruded rod of the second or third fuel systems,i.e. a cement/carbon fuel source or the partially organic fuel system,the aerosol generating means may be an annulus of cut aerosol generatingmaterial or a roll of such material, rolled to provide a sufficientannular density to support the fuel rod, while still allowing air to bedrawn through the article by the smoker.

[0082] A preferred option is to provide the rod filler material as a cutfiller material. In one case, there may be provided a central core ofcut fuel material surrounded by an annulus of cut aerosol generatingmaterial. This arrangement can also be provided with the aerosolgenerating means as the core material and the fuel source as the annulusmaterial. Known techniques for producing co-axial structures for cutfiller material can be used, e.g. providing a small dimension firstwrapped rod which is fed to a further garniture and cut filler materialis arranged around the first rod.

[0083] In the alternative, if an aerosol generating fuel source isprovided, discrete cut aerosol generating means may be intimately mixedwith discrete cut fuel source material.

[0084] The overall percentages of mixed cut fuel source material and cutaerosol generating material preferably falls within the range of 30-35%carbon, 5-10% binder, 0-2% fibre, 5-10% plasticiser and 40-60% inorganicmaterial. This range may be comprised of the individual sheets ofmaterial having the following compositions:

[0085] Fuel source: 60-70% carbon, 7% propylene glycol alginate binder,1% fibre and 32-22% perlite inorganic material.

[0086] Aerosol generating means: 7% propylene glycol alginate binder, 1%fibre, 15% glycerol plasticiser and 77% perlite inorganic material.

[0087] These materials would typically be mixed in the ratio of 1:1.Other ratios of mixing could be used to give the desired overall rangeof components described above.

[0088] If the aerosol generating means and fuel source are actuallycombined together chemically, the sheet material may be cut and providedwithin the outer wrapper as cut filler material. It may be desirable toincrease the proportion of fuel material in a further combined sheetmaterial, and to provide this material as a central region of highercarbon density surrounded by a less carbon-containing combined cut sheetmaterial.

[0089] When the fuel and aerosol components are produced by extrusionmethods, they may be provided as rods, strands or filaments. A coaxialcore of several strands (or rods or filaments) may be provided of fuelmaterial surrounded by an annulus of gathered strands of aerosolgenerating means. The vice versa arrangement is also possible as above.A further arrangement is the intimate inter-mixing of strands ofdiscrete fuel source and aerosol generating means within the outerwrapper. The rods, strands or filaments may also be comprised of thechemically combined aerosol generating fuel source material. Theseextruded rods, strands or filaments may all be somewhat foamed, ifdesired.

[0090] Where foaming to provide a cellular structure is desired, a coreof foamed fuel source may be surrounded by an annulus of foamed aerosolgenerating means. This may be produced by co-extrusion techniques usingcross-head dies, for example. The vice versa arrangement is alsopossible. It is also possible in all of the above structural embodimentsthat only one of the core or annulus material is foamed.

[0091] Smoking Article

[0092] Advantageously the smoking article incorporates a filter elementwhich may be conventional fibrous cellulose acetate, polypropylene orpolyethylene material or gathered paper material. Multiple filterelements may also be utilised. Filter elements having particularpressure drop characteristics, such as the filter sold by Filtrona andknown as The Ratio Filter, may also be utilised. Disposed upon or withinthe material of the filter element may be further flavouring materials,as described above, which are released or eluted from the filter elementby the aerosol generated by the heated or burnt aerosol generationmeans.

[0093] Disposed about the fuel source at the mouthend thereof and/orbetween the fuel source and the filter element may be a firebreak; Thefirebreak may suitably comprise a more densely packed region of thematerial comprising the aerosol generating means. Preferably thefirebreak also comprises aerosol forming means to enhance the deliveryof aerosol to the smoker, as well as protecting the smoker frompotentially over-hot smoke as the length of the smoking articledecreases. Alternatively, the firebreak may comprise a band of burnretarding material on the exterior of the wrapper, for example. Thefirebreak may be substantially combustible or substantiallynon-combustible material.

[0094] The proportions of the non-inorganic materials are selected togive a smoking article which exhibits extremely low visible sidestreamsmoke. A conventional smoking article comprises cut tobacco wrapped in apaper wrapper. A smoking article which exhibits low visible sidestreamsmoke is required to give a reduction of at least 30% in rate ofsidestream particulate matter, known as NFDPM (nicotine free, dryparticulate matter) emission, in order for there to be a reduction invisible sidestream which is visible to the naked eye. European PatentApplication, Publication No. 0 404 580 describes a smoking articlehaving a paper wrapper which is extremely effective in reducing visiblesidestream smoke. Reductions in visible sidestream particulate matter ofup to 60% against control cigarettes without the inventive papers areachievable with smoking articles incorporating the paper according tothat application. When smoking articles according to the presentinvention and cigarettes according to EPA-0 404 580 are smoked head tohead, smoking articles according to the present invention have even lessvisible sidestream than the cigarettes of EPA 0 404 580. Smokingarticles of the present invention are thus effective to provide visiblesidestream reductions far greater than any other smoking articleavailable at the present time.

[0095] Smoking articles according to the present invention preferablycomprise at least 50% by weight of the article as inorganic material.

[0096] In order that the present invention may be easily understood andreadily carried into effect, reference will now be made, by way ofexample to the following diagrammatic drawings, in which:

[0097]FIG. 1 shows, in longitudinal cross-section, a smoking articleaccording to the present invention,

[0098]FIG. 1a shows, in axial cross-section, another embodiment of asmoking article according to FIG. 1,

[0099]FIG. 2 shows, in longitudinal cross-section, a further smokingarticle according to the present invention,

[0100]FIG. 3 shows, in longitudinal cross-section a yet furtherembodiment according to the present invention, and

[0101]FIG. 4 shows another embodiment of the present invention inlongitudinal cross-section.

[0102] One embodiment of a smoking article of the present invention isdepicted in FIG. 1 of the drawings hereof. FIG. 1 shows a cigarette 1comprising a smoking material rod 2 and a filter element 3. The filterelement 3 is composed of conventional fibrous cellulose acetate tow butmay be of any other type of fibrous material with conventional pressuredrop and filtration efficiency, or a high pressure drop, low filtrationefficiency, non-fibrous material, if appropriate. The filter element 3is attached to the smoking material rod 2 by a tipping wrapper 4. Thefilter element 3 may be ventilated, either using ventilationperforations produced by laser for example, or by means of the naturalpermeability of the tipping wrapper 4 and any underlying plugwrap. Thesmoking material rod 2 comprises an exterior wrapper 5, a co-axiallylocated combustible fuel source 6 and cut smoking material 7 disposedbetween the fuel source 6 and the wrapper 5.

[0103] The exterior wrapper 5 comprises 1% fibre, 4% propylene glycolalginate as a combustible binder, 5% glycerol as a plastisicer and 90%perlite as an inorganic non-combustible filler material. The exteriorwrapper 5 has a white colour, is about 1 mm in thickness, and looks verysimilar to the paper wrapper of a conventional smoking article, orcigarette.

[0104] The co-axial fuel source 6 was produced in accordance with thefirst fuel system above by pyrolysing a circular rod of balsa woodhaving a diameter of about 4 mm. The shape of the balsa wood rod isideal for the purpose of providing an elongate, circular fuel source.The pyrolysed rod has an acceptable strength and is quite robust whensurrounded by the cut smoking material 7. The density of the initialrod, and also in its final form, is important. We have found that if thefuel source is too dense after pyrolysation insufficient oxygen reachesthe interior thereof and therefore the fuel source will not continue toburn. On the other hand, if the density of the pyrolysed fuel source istoo low then the fuel source combusts too actively and thus too rapidly.Balsa and ash have been found to be the more suitable woods for use inthis invention, though other wood species may be found to beappropriate.

[0105] The smoking material 7 is an aerosol generating means consistingof a high proportion of non-combustible, inorganic material, namely 80%perlite, 12% glycerol aerosol forming means, 7% propylene glycolalginate binder and 1% fibre, i.e. the partially inorganic system. Thesmoking material is produced by forming a slurry of the components andmaking a reconstituted sheet in accordance with standard sheet makingtechniques. The sheet of reconstituted inorganic material is then cut toprovide cut filler material 7 and is disposed about the pyrolysed balsawood fuel source 6.

[0106] At the mouth end of the smoking article there is located a region9 of aerosol generating means onto which has been deposited flavouringagents, such as vanilla and toffee, for example. More of theseflavouring agents were disposed within the filter element 3.

[0107] In operation, the cigarette 1 is lit and the cigarette burnsalong the fuel source length producing very little visible sidestreamsmoke. The visible sidestream smoke produced is derived from the organiccomponents in the smoking article and is most visible at the end of apuff. The substantially non-combustible wrapper chars to produce afrangible, white ash, similar to conventional cigarette ash and whichcan be tapped off by the smoker, as required. The non-combustibleexterior wrapper 5 upon charring also produces a dark burn line whichadvances along the smoking article as burning progresses. The smokingarticle burns back along the fuel source 6. As burning occurs an aerosolis produced from the aerosol-generating cut smoking material 7, whichaerosol is drawn into the smoker's mouth. The aerosol, in this instance,is predominantly glycerol and water but also comprises vanilla andtoffee flavours. Other flavours such as tobacco extracts, nicotinecompounds, or other tobacco-like flavours, give the aerosol anacceptable taste and quality but without burning any tobacco material.Additional flavour material is also carried on the filter element, whichmaterial is designed to be released upon the approach of ‘smoke’ oraerosol from the burning aerosol-generating smoking material rod 2,Filter flavourant is not always required if sufficient flavour materialis held in the aerosol generating means.

[0108]FIG. 1a shows a very similar embodiment to FIG. 1 except that inthis cigarette, instead of the smoking material rod 2 incorporating cutsmoking material 7, the smoking material 7′ is present as a rolled sheet8 of smoking material which is rolled about the longitudinal length ofthe fuel source 6. The rolled sheet 8 of the smoking material 7′ isattached by a line or band of adhesive, such as propylene glycerolalginate, extending along the length of the fuel source 6. The rolledsheet 8 of smoking material must be rolled to allow air to pass to theburning coal of the cigarette 1.

[0109] The smoking article 10 depicted in FIG. 2 has a similarstructural arrangement to that of FIG. 1. Identical elements of thecigarette 11 have been given the reference numerals of FIG. 1 increasedby ten.

[0110] In this embodiment the wrapper 15 comprised 1% fibre, 4.5%propylene glycol alginate and 94.5% perlite inorganic, non-combustiblefiller material. No plasticiser was present in the wrapper.

[0111] The fuel source 16 of this embodiment is comprised of combustiblematerial held together with a non-combustible binder. The fuel source 16comprises carbon in the form of pyrolysed coconut fibre, Portland cementand a small amount of potassium nitrate burn promoter in the ratio of8:4:1 respectively. The fuel source 16 was produced by hydrating thecement with a 1.3M solution of potassium nitrate sufficient to form aslurry, adding the powdered carbon to the slurry with a small amount ofdetergent to ‘wet’ the carbonaceous material, and additional water toprovide a slurry of mud-like consistency. A rod of fuel material wasformed by shaping the slurry mixture within a hollow tube, the shapedrod being expelled from within the tube once the rod had sufficientmechanical strength after a period of drying, curing or setting. Anyexcess moisture is driven off by heating after removal from the hollowtube. The fuel source 16 had a diameter of about 4 mm. Surrounded byfiller material 17 the fuel source 16 is quite robust and is well ableto withstand normal handling in the packing process and by the consumer.

[0112] In this embodiment, cocoa flavour was provided at a downstreamlocation of the aerosol generation means 17 and within the filterelement 13.

[0113] The smoking article 20 depicted in FIG. 3 is a further refinementof the embodiment of FIG. 2. Reference numerals referring to identicalelements have again been increased by ten. In this cigarette 21 thesmoking material rod 22 comprises cut smoking material 27 disposed abouta carbon fuel source 26. The exterior wrapper 25 is composed of twolayers. An inner layer 40 is composed of the wrapper material describedin FIGS. 1 and 2. An outer layer 41 is comprised of a coating of avisible sidestream reducing filler, such as magnesium oxide bound by asmall amount of propylene glycol alginate. The proportions of thewrapper in total were 79.5% perlite, 1% fibre, 4.5% propylene glycolalginate and 15% magnesium oxide. The magnesium oxide coating is capableof further reducing the visible sidestream smoke emanating from thesmoking article 10 of FIG. 2, for example. Indeed, the visiblesidestream smoke from smoking article 20 is virtually non-existent.However, the exterior wrapper 25 still produces a dark burn line, theadvance of which enables the smoker to determine whether the cigarette21 is, in fact, alight and to thereby monitor the progress ofcombustion.

[0114] In the alternative to a coating of visible sidestream reducingfiller, the visible sidestream reducing filler may be included in thewrapper furnish to form a single wrapper. A typical composition of thetreated wrapper 25 consists of 87.5% perlite inorganic material, 4%propylene glycol alginate binder, 7.5% magnesium oxide visiblesidestream reducing filler and 1% fibre. Levels of 15% magnesium oxidehave been used effectively with 80% perlite.

[0115] In this embodiment, tobacco extract flavours were disposed withinthe filter element 23.

[0116] The drawing of FIG. 4 shows a further embodiment of the inventionin which reference numerals which refer to the same features as in FIG.3 have been increased by ten. The smoking material rod 32 of cigarette31 comprised a wrapper 35 enclosing cut smoking material which is alsocombined with fuel means to provide an aerosol generating fuel source37. The aerosol generating fuel source 37 together comprises alengthwise extending fuel source and lengthwise aerosol extendinggeneration means. The aerosol generating fuel source 37 comprises 55%carbon (pyrolysed coconut fibre), 12% glycerol aerosol forming means, 7%propylene glycol alginate binder, 1% fibre and 25% perlite inorganicmaterial, i.e. the partially inorganic system. This material is producedusing the reconstituted sheet method described above and casting eitheron a drum or band caster. At one end of the aerosol generating fuelsource 37 there was applied chocolate and mint flavours. Flavourmaterial was also present in the filter element 33.

[0117] Examples of another aerosol generating fuel source from thesecond aerosol generating fuel source system were also producers whichcomprised as little as 10% carbon and 70% perlite inorganic material.The other proportions remained the sane as above.

[0118] The wrapper 35 in this embodiment had the composition of 4.5%propylene glycol alginate binder and 94.5% perlite inorganicnon-combustible filler material in one instance. In another instance,the wrapper had the composition of 4% propylene glycol alginate, 5%glycerol plasticiser and 90% perlite.

[0119] All of the aerosol generating compositions described above may bemodified in colour by replacing up to 10% of the inorganic fillermaterial with a colourant, such as caramel or liquorice or extractsthereof.

[0120] The percentages given in this specification are on a dry weightbasis. The amount of water required to make a suitable slurry of solidcomponents amounting to 500 g (including glycerol) is usually about 1200ml.

[0121] The following tables give further details of embodiments preparedto illustrate the invention.

[0122] Table 1 gives details regarding the influence of materialformulation on the physical properties of the outer.

[0123] A slurry was prepared from hydrated binder and inorganic materialto the recipe given in Table 1. Outer wrappers were made from the slurryto a length of 70 mm and 0.5 mm wall thickness by use of a ram extruder.The outer wrappers were dried at exit from the extruder die by use oftwo intra-red heaters placed 5-10 cm from the extrudate. The physicalproperties of the outer wrappers are detailed in Table 1.

[0124] Table 2 gives details regarding the influence of processconditions on the efficiency of setting outer wrappers using calciumchloride solution.

[0125] A slurry was prepared from 10 g sodium alginate, 45 g chalk and45 g perlite in 200 ml of water. A ram extruder was filled with theslurry and the outer wrappers were prepared by extrusion of the slurrythrough an 8 mm outer diameter, 7 mm inner diameter torpedo die intocalcium chloride solution. Firmness of the outer was judged subjectivelyby a panel of three individuals, on a ten point scale running from 1(indicating that the extrudate was completely unchanged by immersion inthe bath) to 10 (indicating that the extrudate was completely set andrigid).

[0126] The Table illustrates that as the number of uses of the bath isincreased, the firmness of the outer wrapper decreases. The firmness ofthe outer wrapper increases as the concentration of the electrolytesolution increases and as immersion time increases.

[0127] Table 3 gives details of the combustion limits of carbon andglycerol based aerosol generating fuel sources using a single strand ofextruded material of 1.00 mm diameter.

[0128] Table 4 shows the effect of binder type on the combustioncharacteristics of a variety of carbon and glycerol based aerosolgenerating fuel sources using single strands of extruded material of1.00 mm diameter. Some binders are more combustible then others andtherefore influence the proportions of material used in the aerosolgenerating fuel source.

[0129] Table 5 shows the effect of filler type on the combustioncharacteristics of a variety of carbon and glycerol based aerosolgenerating fuel sources using single strands of extruded material of1.00 mm diameter. Some inorganic filler materials facilitate combustionof a range of aerosol generating fuel source mixtures. Chalk is thepreferred filler over the ranges illustrated. This table should notnecessarily be taken to indicate that the fillers used in mixturesoutside these illustrated ranges would not burn.

[0130] The tests performed for Tables 3, 4 and 5 were performed onsingle strands smouldering in free air rather than on a number ofstrands within an outer wrapper in order to exclude any influence on thecombustion of the strands due to the properties of the outer wrapper.

[0131] Table 6 gives smoke yields from filter-tipped cigarettes whichhad the following construction:

[0132] A 5 mm filter was obtained from a State Express Internationalcigarette, the filter comprising fibrous cellulose acetate of 2.8filament denier of Y cross-section, 34,000 total denier and having apressure drop of 13 mm WG.

[0133] The substantially non-combustible outer wrapper was extrudedusing a ram extruder through an 8 mm outer diameter, 7 mm inner diametertorpedo die and the aerosol generating fuel source was extruded as 1.00mm diameter strands from a ram extruder, the strands being gatheredtogether and inserted into dried extruded outer wrappers. The cigaretterod length, i.e. excluding the filter element, was 67 mm. One cigaretteof each was smoked under standard machine smoking conditions in which a35 cm³ puff of two seconds duration is taken every minute.

[0134] The first five examples of Table 4 illustrate that carbon fuelstrands will burn without producing significant levels of totalparticulate matter (TPM) even with organic material (PGA) in the fuelstrands.

[0135] The cigarettes according to the invention have very low visiblesidestream smoke levels. However, the nature of the sidestream smokefrom the inventive articles does not render the conventional fishtailsidestream measuring apparatus described in Analyst, October 1988,Volume 113, pp 1509-1513 a suitable measuring apparatus. We are thusunable to provide yield details in this respect. TABLE 1 Influence ofMaterial Formulation on the Physical Properties of the Outer. Energy %Total required Whiteness % % % Binder Plasticiser solids WaterPermeability to crush of outer Perlite Chalk Binder Type (Glycerol) (g)(g) (CU) outer (J) (DE) 85 15 PGA 100 300 94 22.5 67.5 10 PGA 100 200 145.3 6.6 90 10 PGA 100 200 3.8 5.2 9.2 80 20 PGA 100 200 77 4.6 80 20 PGA100 200 0.6 9.6 97.5 2.5 PGA 100 70 6.5 9.2 95 5 PGA 100 40 4.5 9.5 7525 PGA 100 500 110.7 75 25 PGA 100 260 90 10 PGA 100 200 90 10 HEC 100150 cnm 5.2 3.7 45 45 10 HEC 100 130 57 45 45 10 AA 100 120 21 90 10 AA100 135 160 88 10 PGA 2 100 180 185 85 10 PGA 5 100 160 145 80 10 PGA 10100 140 215 70 10 PGA 20 100 135 105 72 8 PGA 20 100 120 cnm 75 5 PGA 20100 115 cnm 77.5 2.5 PGA 20 100 110 90 10 SCMC 100 14 95 5 SCMC 100 7017.5 4.4 97.5 2.5 SCMC 100 110 34 3.8 85 15 SCMC 100 2.9 77.5 9 13.5SCMC 100 100 12 85 5 10 PGA 100 161 9.3 70 20 10 PGA 100 120 9.2 65 2510 PGA 100 79 40 50 10 PGA 100 19.5 12 45 45 10 HPC 100 95 111 90 10 NaA100 160 65 45 45 10 NaA 100 120 6 90 10 NaCaA 100 205 70.7 45 45 10NaCaA 100 190 90 10 Karaya 100 175 285 gum 45 45 10 Karaya 100 130 cnmgum 90 10 Locust 100 150 295 bean gum 45 45 10 Locust 100 130 60 beangum 45 45 10 Acacia 100 8 gum

[0136] TABLE 2 Influence of Process Conditions on the Efficiency ofSetting Outer Wrappers using Calcium Chloride solution. Calcium chlorideImmersion Number of uses of Subjective solution strength time in thebath prior to firmness (M 1⁻¹) bath(s) this measurement of outer. 0 0 01 1 2 0 4 1 4 0 6.5 1 6 0 7.5 1 8 0 8 1 10 0 8 1 60 0 9.5 0.1 10 0 2.50.5 10 0 4.7 1 10 0 6.7 2 10 0 7.7 1 10 1 7 1 10 2 6 1 10 3 6 1 10 4 5 110 5 5 1 10 6 4 1 10 7 3.6 1 10 8 3

[0137] TABLE 3 Combustion Limits of Carbon and Glycerol Based AerosolGenerating Fuel Source (as single strand) Fuel Combustions that burnFuel Combustions that do not burn % % % % % % % % Carbon Glycerol PGAChalk Carbon Glycerol PGA Chalk 0 10 10 80 4 10 10 76 5 20 10 65 5 20 1065 7 20 10 63 8 26 10 56 8 5 10 77 8 30 10 52 8 10 10 72 8 15 10 67 821.5 10 60.5 9 15 10 66 9 20 10 61 10 15.5 10 64.5 10 0 10 80 10 10 1070 11 15 10 64 11 3 10 76 11 20 10 59 11 11 10 68 11 21 10 58 11 30 1049 12 8 10 70 12 0 10 78 12 9 10 69 12 6 10 72 12 10 10 68 12 7 10 71 1211 10 67 13 20 10 57 15 6 10 69 15 0 10 75 15 20 10 55 15 3 10 72 20 610 64 20 0 10 70 20 10 10 60 20 3 10 67 30 0 10 60 30 3 10 57 30 6 10 5450 0 10 40

[0138] TABLE 4 Influence of binder type on the combustioncharacteristics of various aerosol generating fuel source mixtures.Binder Type Propylene Hydroxy Glycol Sodium Calcium Propyl AlginateAlginate Alginate Pectin Cellulose 8% Carbon No Yes No No Yes 11%Glycerol 71% Chalk 10% Binder 12% Carbon Yes Yes No Yes Yes 11% Glycerol67% Chalk 10% Binder 16% Carbon Yes Yes No Yes No 11% Glycerol 63% Chalk10% Binder 8% Carbon Yes Yes No Yes Yes 11% Glycerol 61% Chalk 20%Binder 32% Carbon Yes Yes No Yes Yes 11% Glycerol 57% Chalk 20% Binder16% Carbon Yes Yes No Yes Yes 11% Glycerol 53% Chalk 20% Binder 8%Carbon Yes No No Yes — 11% Glycerol 51% Chalk 30% Binder 12% Carbon YesNo No Yes — 11% Glycerol 47% Chalk 30% Binder 16% Carbon Yes No No Yes —11% Glycerol 43% Chalk 30% Binder

[0139] TABLE 5 Influence of inorganic, filler type on the combustioncharacteristics of various aerosol generating and source mixtures.Filler Type Magnesium Calcium Magnesium Perlite Oxide Bentonite ChalkSulphate hydroxide Kieselguhr Fuel Mixture 18.2% Carbon, No No No Yes NoNo Yes 11.4% PGA, 12.5% Glycerol, 58% Filler 16.3% Carbon, No No No YesNo No Yes 10.2% PGA, 11.2% Glycerol, 62.2% Filler 15.8% Carbon, No No NoYes No No — 13.2% PGA, 14.5% Glycerol, 56.5% Filler 14.8% Carbon, No —No Yes No No No 9.3% PGA, 10.2% Glycerol, 65.7% Filler 13.9% Carbon, No— No Yes No No No 11.6% PGA, 12.8% Glycerol, 61.6% Filler 12.5% Carbon,— No — Yes No No No 10.4% PGA, 11.5% Glycerol, 65.6% Filler 10.5%Carbon, No No No Yes — No No 13.2% PGA, 14.5% Glycerol, 61.8% Filler9.3% Carbon, — No No No — No No 11.6% PGA, 12.8% Glycerol, 66.3% Filler8.3% Carbon, No — — No — No No 10.4% PGA, 11.5% Glycerol, 69.8% Filler

[0140] TABLE 6 Smoke yields from filter tipped cigarettes illustratingthe invention Weight % % Sodium Weight % % % % PGA Puff TPM Glycerol (g)Perlite Alginate (g) Carbon Glycerol Chalk Binder number (mg) (mg)0.6035 90 10 0.5865 12 0 78 10 DNB 0.0 0 0.4025 90 10 0.7255 15 0 75 105 0.0 0 0.4535 90 10 0.7291 20 0 70 10 10 0.2 0 0.4774 90 10 0.6896 30 060 10 6 0.0 0 0.3812 90 10 0.5973 50 0 40 10 5 0.1 0 0.6001 90 10 0.68478 5 77 10 DNB 0.0 0 0.6344 90 10 0.7186 12 6 72 10 7 4.3 2 0.6555 90 100.7691 15 6 69 10 7 3.3 1 0.6777 go 10 0.6818 20 6 64 10 8 3.0 <1 0.473090 10 0.7691 30 6 54 10 6 2.2 <1 0.6312 90 10 0.6530 40 6 44 10 8 1.9 <10.5103 90 10 0.4808 12 8 70 10 9 1.3 <1 0.5845 90 10 0.6990 4 10 76 10DNB 0 0 0.6219 90 10 0.7192 8 10 72 10 6 3.8 2 0.5060 90 10 0.6780 10 1070 10 DNB 0 0 0.4872 90 10 0.6916 11 10 69 10 5 4.3 3 0.6035 90 100.5865 12 10 68 10 DNB 0 0 0.5665 90 10 0.6215 9 15 66 10 8 5.7 2 0.483890 10 0.7133 10 15.5 64.5 10 7 5.4 3 0.5161 90 10 0.7092 11 15 64 10 67.5 3 0.6103 90 10 0.6443 8 21.5 60.5 10 6 6.4 3 0.4461 90 10 0.7446 826 56 10 6 12.7 6

1. A smoking article having a smoking material rod comprising asubstantially non-combustible wrapper extending substantially along thelength of the smoking material rod and enwrapping smoking material, saidsmoking material comprising a combustible fuel source extendingsubstantially along the length of the smoking material rod and aerosolgenerating means extending substantially along the length of the smokingmaterial rod, characterised in that said wrapper is comprised ofpredominantly non-combustible, particulate, inorganic filler material, abinder, optionally a plasticiser, and optionally a small amount ofcellulosic fibre material, and said inorganic filler material is atleast 65% by weight of said wrapper.
 2. A smoking article having asmoking material rod comprising a substantially non-combustible wrapperextending substantially along the length of the smoking material rod andenwrapping smoking material, said smoking material comprising acombustible fuel source extending substantially along the full length ofthe smoking material rod, and aerosol generating means being disposedbetween the fuel source and the wrapper and extending substantiallyalong the length of the smoking material rod, characterised in that saidwrapper is comprised of predominantly non-combustible, particulate,inorganic filler material, a binder, optionally a plasticiser, andoptionally a small amount of cellulosic fibre material, and saidinorganic filler material is at least 65% by weight of said wrapper. 3.A smoking article according to claims 1 or 2, wherein the fuel sourceand/or the aerosol generating means comprise longitudinally extendingrods, strands or filaments.
 4. A smoking article according to claims 1or 2, wherein the fuel source comprises cut filler material.
 5. Asmoking article according to claims 1 or w, wherein the fuel sourceand/or the aerosol generating means comprise a rolled sheet.
 6. Asmoking article according to any one of claims 1 to 4 wherein theaerosol generating means is cut filler material.
 7. A smoking articleaccording to any one of claims 1-4 or wherein the fuel source and theaerosol generating means both comprise cut filler material.
 8. A smokingarticle according to claim 7, wherein the cut filler materials areintimately mixed.
 9. A smoking material according to claim 1 or 2,wherein aerosol generating means and the fuel source are combined toprovide an aerosol generating fuel source.
 10. A smoking article asclaimed in any one of claims 1 to 7, wherein the aerosol generatingmeans and the fuel source comprise a core and annulus arrangement.
 11. Asmoking article according to any one of claims 1-10, wherein the aerosolgenerating means and the duel source comprise a core and annulusarrangement of foamed components.
 12. A smoking article according toclaim 1 or 2, wherein one of the fuel source or aerosol generating meansis foamed.
 13. A smoking article according to any one of claims 1 to 12,wherein the smoking article further comprises a filter element.
 14. Asmoking article according to any one of claims 1 to 13, wherein at least50% by weight of the article is inorganic material.
 15. A smokingarticle according to any one of claims 1 to 10, wherein the wrapper hasthe features of any one of claims 20 to
 42. 16. A smoking articleaccording to any one of claims 1 to 10, wherein the fuel source has thefeatures of any one of claims 43 to
 58. 17. A smoking article accordingto any one of claims 1 to 10, wherein the aerosol generating means hasthe features of any one of claims 59 to
 72. 18. A smoking articleaccording to claim 9, wherein the aerosol generating fuel source has thefeatures of any one of claims 73 to
 85. 19. A smoking article producedaccording to the method of any one of claims 86 to
 95. 20. Asubstantially non-combustible smoking article wrapper comprised ofpredominantly non-combustible, particulate, inorganic filler material, abinder, optionally a plasticiser, and optionally a small amount ofcellulosic fibre material, said inorganic filler material being at least65% by weight of said wrapper.
 21. A substantially non-combustiblesmoking article wrapper according to claim 20, wherein saidnon-combustible inorganic filler material is a non-metallic material.22. A wrapper according to any one of claims 20 or 21, herein saidnon-combustible inorganic filler material is one or more of perlite,vermiculite, diatomaceous earth, colloidal silica, chalk, magnesiumoxide, magnesium sulphate, magnesium carbonate, or other low density,non-combustible inorganic filler materials.
 23. A wrapper according toclaim 20, wherein the inorganic filler material comprises at least 90%by weight of the wrapper.
 24. A wrapper according to claim 24, whereinthe inorganic filler material comprises at least 80% by weight of thewrapper.
 25. A wrapper according to claim 24, wherein the inorganicfiller material comprises at least 90% by weight of the wrapper.
 26. Awrapper according to any one of claims 20 to 25, wherein the wrappercomprises less than 10% fibre material by weight of, the wrapper.
 27. Awrapper according to any one of claims 20 to 26, wherein the wrappercomprises a binder and/or a plasticiser at up to 30% by weight of thewrapper.
 28. A wrapper according to claim 27, wherein the binder is notpresent at more than 25% by weight of the wrapper.
 29. A wrapperaccording to claim 27 or 28, wherein the binder is present at about8-10% by weight of the wrapper.
 30. A wrapper according to claim 27 or28, wherein the binder is present at about 5% or less by weight of thewrapper.
 31. A wrapper according to any one of claims 27 to 30, whereinthe binder is an organic binder selected from one or more of the classesof cellulose derivatives, cellulose ethers, alginic binders, gums, gels,pectins or starches.
 32. A wrapper according to claim 31, wherein theorganic binder is one or more of sodium carboxymethyl cellulose, methylcellulose, hydroxypropyl cellulose, hyroxyethyl cellulose, ammoniumalginate, sodium alginate, sodium calcium alginate, calcium ammoniumalginate, potassium alginate, magnesium alginate, triethanol-aminealginate, propyliene glycol aluminate, aliminium alginate, copperalginate, zinc alginate, silver alginate, gum arabic, gum ghatti, gumtragacanth, Karaya gum, locust bean gum, acacia gum, guar gum, quinceseed gum, xanthan gum, agar, agarose, carrageenans, fucoidan orfurcelleran.
 33. A wrapper according to any one of claims 27 to 30,wherein the binder is an inorganic, non-combustible binder.
 34. Awrapper according to claim 33, wherein the binder is ore or more ofpotassium silicate, magnesium oxide in combination with potassiumsilicate, or cement.
 35. A wrapper according to claim 27, wherein theplasticiser is present at up to 20% by weight or the wrapper.
 36. Awrapper according to claim 35, wherein the plasticiser is present atabout 10% no less by weight of the wrapper.
 37. A wrapper according toclaim 36, wherein the plasticiser is present at about 5% or less byweight of the wrapper.
 38. A wrapper according to any one of claims 27to 37, wherein the plasticiser is one or more of glycerol, propyleneglycol, low melting point fats or low melting point oils.
 39. A wrapperaccording to any one of claims 20 to 38, wherein the permeability ofsaid wrapper is within the range of 1-150 Coresta Units.
 40. A wrapperaccording to any one of claims 20 to 39, wherein the wrapper comprises adeodoriser selected from citronellal, geraniol or vanillin.
 41. Asmoking article fuel source of substantially the whole length of asmoking article, the fuel source comprising carbonaceous material, aninorganic non-combustible binder and optionally a burn promoter.
 42. Asmoking article according to claim 41, wherein said inorganicnon-combustible binder comprises one or more of potassium silicate,magnesium oxide in combination with potassium silicate or cement, suchas Portland cement.
 43. A smoking article fuel source according to claim41 or 42, wherein said inorganic non-combustible binder is presentwithin the range of 10-65% by weight of the fuel source.
 44. A smokingarticle fuel source according to claim 43, wherein the binder is presentat less than 40% by weight of the fuel source.
 45. A smoking articlefuel source according to any one or claims 41 to 44, wherein the fuelsource comprises 5-20% by weight thereof of a burn promoter.
 46. Asmoking article fuel source according to any one of claims 41 to 45,wherein the fuel source comprises 25-70% carbon by weight thereof.
 47. Asmoking article fuel source according to claim 46, wherein the fuelsource comprises at least 55% carbon weight thereof.
 48. A smokingarticle fuel source according to claim 41, wherein the fuel sourcecomprises about 30% carbon, 60% inorganic, non-combustible binder andless than about 10% burn promoter.
 49. A smoking article fuel source ofsubstantially the whole length of a smoking article, the fuel sourcecomprising 15-70% carbon, 84-5% non-combustible inorganic fillermaterial, 0-5% plasticiser, 1-20% organic binder and 0-20% inorganicbinder, the plasticiser comprising one or more of low melting point fatsor low melting point oils.
 50. A smoking article fuel source accordingto claim 49, wherein carbon is present within the range of 25-35% byweight of the fuel source.
 51. A smoking article fuel source accordingto any one of claims 49 or 50, wherein the non-combustible inorganicfiller material comprises one or more of perlite, vermiculite,diatomaceous earth, colloidal silica, chalk, magnesium oxide, magnesiumsulphate, magnesium carbonate or other low density, non-combustibleinorganic filler materials.
 52. A smoking article fuel source accordingto any one of claims 49 to 51, wherein the organic binder is selectedfrom one or more of the classes of cellulose derivatives, celluloseethers, alginic binders, gums, gels, pectins or starches.
 53. A smokingarticle fuel source according to claim 52, wherein the organic binder issodium carboxymethyl cellulose, methyl cellulose, hydroxypropylcellulose, hydroxyethyl cellulose, ammonium alginate, sodium alginate,sodium calcium alginate, calcium ammonium alginate, potassium alginate,magnesium alginate, triethanol-amine alginate, propylene glycolalginate, aluminium alginate, copper alginate, zinc alginate, silveralginate, gum arabic, gum ghatti, gum tragacanth, Karaya gum, locustbean gum, acacia gum, guar gum, quince seed gum, xanthan gum, agar,agarose, carrageenans, fucoidan or furcelleran.
 54. A smoking articlefuel source according to any one of claims 49 to 51, wherein theinorganic binder is one or more of potassium silicate, magnesium oxidein combination with potassium silicate or cement.
 55. A smoking articleaerosol generating means comprising a non-combustible inorganic fillermaterial, aerosol forming means, and an organic or inorganic binder. 56.A smoking article aerosol generating means according to claim 55,wherein the aerosol generating means comprises 95-30% inorganic,non-combustible binder, 45-90% non-combustible inorganic filler materialand 5-30% aerosol forming means.
 57. A smoking article aerosolgenerating means according to claim. 55, wherein the aerosol generatingmeans comprises 1-25% organic binder, 50-94% non-combustible inorganicfiller material, and 5-30% aerosol forming means.
 58. A smoking articleaerosol generating means comprising an organic filler material, aerosolforming means, an organic binder and optionally a non-combustibleinorganic filler material.
 59. A smoking article aerosol generatingmeans according to claim 58, wherein the aerosol generating meanscomprises 1-25% organic binder, 1-94% organic filler material, 0-93%inorganic filler material and 5-30% aerosol forming means.
 60. A smokingarticle aerosol generating means according to any one of claims 55 to59, wherein the non-combustible inorganic filler material is one or moreof perlite, vermiculite, diatomaceous earth, colloidal silica, chalk,magnesium oxide, magnesium sulphate, magnesium carbonate, dr other lowdensity, non-combustible inorganic filler materials.
 61. A smokingarticle aerosol generating means according to any one of claims 55-60,wherein the organic filler material comprises inorganic salts of organicacids, or polysaccharide material.
 62. A smoking article aerosolgenerating means according to any one of claims 55-61, wherein theaerosol forming means comprises one or more of polyhydric alcohols,esters, or high boiling point hydrocarbons.
 63. A smoking articlegenerating means according to claim 62, wherein the aerosol formingmeans is one or more of glycerol, propylene glycol, triethylene glycol,triethyl citrate or triacetin.
 64. A smoking article aerosol generatingmeans according to any one of claims 55 to 63, wherein the organicbinder is selected from one or more of the classes of cellulosederivatives, cellulose ethers, alginic binders, gums, gels, pectins orstarches.
 65. A smoking article aerosol generating means according toclaim 64, wherein the organic binder is one or more of sodiumcarboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose,hydroxyethyl cellulose, ammonium alginate, sodium alginate, sodiumcalcium alginate, calcium ammonium alginate, potassium alginate,magnesium alginate, triethanol-amine alginate, propylene glycolalginate, aluminium alginate, copper alginate, zinc alginate, silveralginate, gum arabic, gum ghatti, gum tragacanth, Karaya gum, locustbean gum, acacia gum, guar gum, quince seed gum, xanthan gum, agar,agarose, carrageenans, fucoidan or furcelleran.
 66. A smoking articleaerosol generating means according to claim 55 or 56, wherein theinorganic binder comprises one or more of one or more of potassiumsilicate, magnesium oxide in combination with potassium silicate, orcement.
 67. A smoking article aerosol generating means according toclaim 58 or 59 wherein the aerosol generating means comprises anexpansion medium
 68. A smoking article aerosol generating meansaccording to any one of claims 55-67, wherein the aerosol generatingmeans comprises flavouring agents.
 69. A smoking article aerosolgenerating fuel source comprising a non-combustible inorganic fillermaterial, aerosol forming means, an organic or inorganic binder carbon.70. A smoking article aerosol generating fuel source according to claim69, wherein the aerosol generating source comprises 0-35% inorganicfiller material, 5-30% aerosol forming means, 30-60% inorganic binder,30-65% carbon and 0-10% burn promoter.
 71. A smoking article aerosolgenerating fuel source according to claim 69, wherein the aerosolgenerating fuel source comprises 86-0% inorganic filler material, 5-30%aerosol forming means, 1-25% organic binder and 8-60% carbon.
 72. Asmoking article aerosol generating fuel source comprising organic fillermaterial, optionally a non-combustible inorganic filler material,aerosol forming means, organic binder and carbon.
 73. A smoking articleaerosol generating fuel source according to claim 72, wherein theaerosol generating fuel source comprises 93-0% organic filler material,0-93% inorganic filler material, 5-30% aerosol forming means, 1-25%organic binder and 1-60% carbon.
 74. A, smoking article aerosolgenerating fuel source according to any one of claims 69 to 73, whereinnon-combustible inorganic filler material comprises one or more ofperlite, vermiculite, diatomaceous earth, colloidal silica, chalk,magnesium oxide, magnesium sulphate, magnesium carbonate or other lowdensity, non-combustible inorganic filler materials.
 75. A smokingarticle aerosol generating fuel source according to any one of claims 72to 74, wherein the organic filler material comprises inorganic salts oforganic acids or polysaccharide material.
 76. A smoking article aerosolgenerating fuel source according to any one of claims 69 to 75, whereinthe aerosol forming means comprises one or more of polyhydric alcohols,esters, or high boiling point hydrocarbons.
 77. A smoking articleaerosol generating fuel source according to claim 76, wherein theaerosol forming means is one or more of glycerol, propylene glycol,triethylene glycol, triethyl citrate or triacetin.
 78. A smoking articleaerosol generating fuel source according to claim 69 or 70 wherein theinorganic binder comprises one or more of potassium silicate, magnesiumoxide in combination with potassium silicate or cement.
 79. A smokingarticle aerosol generating fuel source according to any one of claims 69and 71 to 78, wherein the organic binder is selected from one or more ofthe classes of cellulose derivatives, cellulose ethers, alginic binders,gums, gels, pectins or starches.
 80. A smoking article aerosolgenerating fuel source according to claim 79, wherein the organic binderis one or more of sodium carboxymethyl cellulose, methyl cellulose,hydroxypropyl cellulose, hydroxyethyl cellulose, ammonium alginate,sodium alginate, sodium calcium alginate, calcium ammonium alginate,potassium alginate, magnesium alginate, triethanol-amine alginate,propylene glycol alginate, aluminium alginate, copper alginate, zincalginate, silver alginate, gum arabic, gum ghatti, gum tragacanth,Karaya gum, locust bean gum, acacia gum, guar gum, quince seed gum,xanthan gum, agar, agarose, carrageenans, fucoidan or furcelleran.
 81. Asmoking article aerosol generating fuel source according to any one ofclaims 72 or 73, wherein the aerosol generating fuel source comprises anexpansion medium.
 82. A method of producing a substantiallynon-combustible smoking article wrapper comprising predominantlynon-combustible inorganic filler material and a binder, the methodcomprising producing a mixture of the non-combustible inorganic fillermaterial and a binder, extruding the mixture to provide a hollow tube,and contacting the hallow tube with a material which causes the hollowtube to set rapidly.
 83. A method according to claim 82, wherein saidmaterial which causes said hollow tube to set is either a waterscavenging substance which removes water contained in said tube, asolution which renders a soluble binder in said mixture of said tubeinsoluble, or a hydrophilic substance which removes water from anaqueous-containing mixture of said tube.
 84. A method according to claim82 or 83, wherein the extrusion process occurs at not more than 3-4 bar(300-400 kPa) at the extruder die of a ram extruder.
 85. A methodaccording to claim 82 or 83, wherein the extrusion process occurs at notmore than 9 bar (900 kPa) when using a screw extruder.
 86. A methodaccording to claim 83, wherein the water scavenging substance is lightmagnesium oxide.
 87. A method according to claim 83, wherein a solublealginate is rendered insoluble by the addition of solubilising agents,such as ammonium hydroxide or calcium chloride.
 88. A method accordingto claim 83, wherein the hydrophilic substance is ethanol.
 89. A methodaccording to any one of claims 82-88, wherein pre-extrusion asub-critical level of precipitating agent is present in the extruderbarrel and post extrusion the level of precipitating agent is increasedto a critical level to cause complete precipitation.
 90. A methodaccording to claim 82, wherein the method comprises sequentialapplication of said processes.
 91. A method according to any one ofclaims 82 to 83, wherein the wrapper mixture comprises sacrificialmolecules which can be removed after the formation of said wrapper byapplication of heat or chemical reaction.
 92. A smoking article having asmoking material rod comprising a substantially non-combustible wrapperextending substantially along the length of the smoking material rod andenwrapping a combustible fuel source extending substantially along thelength of the smoking material rod and aerosol generating meansextending substantially along the length of the smoking material rod.93. A smoking article having a smoking material rod comprising asubstantially non-combustible wrapper extending substantially along thelength of the smoking material rod and enwrapping a combustible fuelsource extending substantially along the full length of the smokingmaterial rod, and aerosol generating means being disposed between thefuel source and the wrapper and extending substantially along the lengthof the smoking material rod.